Many electrical connectors are of a general type commonly called vertical-mount connectors, wherein the connectors are mounted to a surface of a printed circuit board. The connectors mount terminals which often have solder tail portions projecting from a lower face of a connector housing and into respective holes in a printed circuit board for soldering to circuit traces on the board and/or in the holes. The connectors often are mounted to a top surface of the board, and the terminals are wave soldered from a bottom surface of the board.
Various systems have been used to prevent "wicking" of the solder material up the solder tails and into the connector where the solder material will contaminate contact portions of the terminals, such as receptacle portions of the terminals, and interfere with proper interconnections between the terminals and other electrical components, such as male terminals inserted into the receptacle portions. For instance, predetermined areas of the terminals, such as between the solder tail portions and the contact portions thereof, have been selectively plated with materials which do not adhere to the solder material, or "repels" the solder material, whereby the solder material cannot migrate up the terminals and contaminate the contact portions.
Other approaches have included mounting the contact portions of the terminals in cavities of the connector housing and using plugs or other barriers to close bottom openings to the cavities, whereby the solder material cannot contaminate the terminal contact portions. Both the selective plating and the plug or barrier solutions to the wicking problem are relatively expensive procedures or constructions, particularly in compact high density connectors used in miniaturized electronic circuitry. In addition, plugs or barriers may cause other problems because they seal-off lower ends of the terminal-receiving cavities wherein contaminating moisture can accumulate.
An example of a connector construction in which wicking is quite prevalent is a connector which includes a dielectric housing mounted to a surface of a printed circuit board. The housing includes a plurality of cavities mounting receptacle-type contact portions of a plurality of terminals. Solder tails project from the receptacle portions of the terminals, past openings of the cavities at the bottom of the housing, and into plated through holes in a printed circuit board. The receptacle or contact portions are adapted to receive male terminals or other complementary mating electrical components. For instance, the receptacle portions of the terminals may have a generally box-like configuration in cross-section. The solder material has a tendency to wick up the terminals and upwardly along the receptacle portions in a "chimney" affect. During a wave soldering operation, the solder material has a tendency to be pulled up the terminal by the cleaners and fluxes used in the processes, particularly where the holes in the printed circuit board are through plated. For some years, wave soldering of these connector designs have employed Halogens as cleaners and fluxes which are controllable to a degree by the aforesaid selective plating processes or the use of anti-wicking plugs or barriers which, again, are quite expensive systems.
Today, for environmental reasons, there is a trend or movement away from the use of Halogens as cleaners and fluxes, and to the use of new types of organic chemicals which are much more active (i.e. more acidic) but which have magnified the solder wicking problem, because these chemicals attract the solder material to a greater extent than Halogens. Therefore, there is a need for a much more simple solution to the anti-wicking problem than that afforded by expensive selective plating procedures and plug or barrier constructions. This invention is directed to satisfying that need and solving the problems outlined above.